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Tag Archives: diabetes

Friday Science Review: April 9, 2010

New fixes for diabetes, HIV, and nerve damage…

Nano-Vaccine Cures Diabetes: To prevent the immune system from attacking pancreatic cells in Type 1 diabetes, a nanotechnology based “vaccine” was used successfully to stop the disease in mice.  The strategy involves nanoparticles that are coated with diabetes specific peptides and bound to MHC molecules. When injected into the body, they stimulate regulatory T cells – the “friendly” T cells that prevent the “bad” T cells from destroying the insulin producing beta cells in the pancreas.  The advantage of this method is that it is specific to the ‘diabetes T cells’ and there are no negative effects on the rest of the immune system.  Other autoimmune diseases may also benefit from a nanoparticle vaccine approach.  Dr. Pere Santamaria’s team at the University of Calgary describes their work in the online edition of Immunity and has licensed this innovative technology to Parvus Therapeutics, Inc., a U of C spin-off company.

Allowing Neural Regeneration: The p75NTR receptor is important for the development of the nervous system during childhood.  A new research study published in Nature Neuroscience describes an inhibitory effect of p75 neurotrophin receptors (p75NTR) in the adult nervous system.  Not only does it prevent adult nerve cells from regenerating, it actively destroys axons as necessary if any aberrant connections try to form.  This monitoring system is likely skewed in neurological diseases or disorders.  Thus, further molecular information surrounding p75NTR in the nervous system can lead to developing strategies to facilitate nerve regeneration to occur or prevent degenerative disorders.  Dr. Freda Miller and her team conducted the research at The Hospital for Sick Children in Toronto.

HIV’s Secret Weapon Revealed: The discovery of how the viral protein called Vpu facilitates HIV-1 proliferation in a host may present opportunities to block this pathway with a small molecule inhibitor.  Vpu binds to and blocks Tetherin, a natural antiviral protein on the cell surface that can sense and capture the virus and prevent production and further transmission of HIV-1.  HIV-1 has evolved with Vpu as its weapon to impede Tetherin from reaching the cell surface where it acts to tether viruses.  Now it is time for scientists to outsmart the virus and find a method to block Vpu.  Dr. Éric A. Cohen directed his team at the Institut de Recherches Cliniques de Montréal and reports the study in this week’s PLoS Pathogens journal.

Cell-Cell Krazy Glue: The integrity of cell-cell contacts is important for the maintenance of the epithelial cell layer and aberrations may contribute to disease progression such as in cancer metastasis.   Two proteins involved in this cell-cell adhesion are p120 catenin and E-cadherin.  Dr. Mitsuhiko Ikura at the Ontario Cancer Institute performed NMR structural studies to provide a detailed map and understanding of the protein-protein interaction between catenin and cadherin.  The detailed study, published in the journal Cell, describe both dynamic and static interactions that contribute to the stability of the adhesion interaction between cells.

Bring out the Bazooka: Following the article above on the epithelial cell layer, this study examines a protein called Bazooka (Par3 in mammalian cells) in fruit flies.  It is expressed on epithelial cells and acts a protein interaction hub to regulate the integrity of the epithelial structure.  Using a series of gene mutants, gene mapping and bioinformatics techniques, researchers identified up to 17 genes that associate with Bazooka to regulate epithelial structure, many of these are novel interactions with Bazooka.  Further study is necessary to determine how they work together and how this translates to human tissues.  The list of genes is available in the article online in PLoS One journal and was reported by lead researcher Dr. Tony Harris at the University of Toronto.

Friday Science Review: February 19, 2010

Hunks and pigs highlight this week’s research wrap-up…

HUNKs Stop Cancer Metastasis: Researchers screening tumour cells found that expression of the enzyme HUNK (Hormonally Up-regulated Neu-associated Kinase) is significantly lower in cancers.  When they reconstituted HUNK into metastatic cancer cells, it decreased their metastastic potential when tested in mouse cancer models.  Its actions block the association of PP2A and cofilin-1 and prevent the formation of actin filaments, which are key skeletal proteins involved in the cell migration process.  Dr. Tak Mak led the research team at the Campbell Family Institute for Breast Cancer Research and published the study in the Proceedings of the National Academy of Sciences.

Malaria Research Gets Genomic Help: A genome-wide study on the parasite Plasmodium falciparum should help researchers in the hunt for new drugs against malaria.  The genome of 189 malaria samples from around the world were decoded and analyzed to try to identify key genes that are responsible for the parasite’s propensity to evolve and become resistant to currently available drug treatments.  These data are invaluable for the design of future therapeutic approaches.  An international team was co-led by Dr. Philip Awadalla at the Université de Montréal and reports their work in the current issue of Nature Genetics.

Genetic Clues to Diabetes: Using a genome-wide association approach, 13 SNPs concentrated in 4 genetic regions were identified to be strongly correlated with glycemic control in type 1 diabetes.  For example, SORCS1 is strongly associated with hypoglycemia (low blood glucose) and BNC2 is correlated with eye and kidney complications.  This study is a first for suggesting that there may be a genetic contribution to the individual’s ability to control blood glucose levels.  The Hospital for Sick Children’s Dr. Andrew Paterson led the study, which appears in the journal Diabetes.

Porky Pig to the Rescue: Scientists revealed a significant advantage to transplanting porcine pancreatic islet cells as a therapeutic for diabetes.  In contrast to using human islet cells, porcine derived cells do not result in the formation of islet amyloids, which allows them to continue functioning properly for the long term.  They attribute this porcine advantage to differences in the sequences of islet amyloid polypeptide (IAPP).  Dr. Bruce Verchere’s team at the University of British Columbia describes their work in the Proceedings of the National Academy of Sciences.

In (un)related news, Guelph University’s genetically engineered pigs or “Enviropigs” were given the OK by Environment Canada as being non-toxic to the environment.  Now they await Health Canada’s nod before they appear in your local supermarket.

Stem Cells Don’t Mind DNA Damage: Canadian scientists have discovered that stem cells intentionally damage their own DNA in order to regulate development… continue reading the rest of the story here at the Stem Cell Network Blog.

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Friday Science Review: February 12, 2010

New Discovery for Neonatal Diabetes: Researchers uncovered an important role for the Rfx6 gene.  Its integrity is required for normal development of the islets of Langerhans cells in the pancreas that produces important hormones including insulin.  Genetic mutations found in Rfx6 are the cause of severe neonatal diabetes where there are no insulin producing islets of Langerhans cells.  To prove the critical role of Rfx6 in directing the differentiation of early pancreatic cells, researchers disrupted the gene in mice and observed the development of an identical disorder as displayed in humans.   Identifying the gene is a key piece of the puzzle and will lead to new avenues to find treatments for all types of diabetes.  Dr. Constantin Polychronakos and his team at McGill University collaborated with researchers from UCSF and report their study in the on-line edition of Nature.

Controlling Stem Cell Fate: A genome-wide screen identified the PCL2 (polycomb-like 2) gene as a key decision maker in determining the fate of stem cells.  This is an important area of research because stem cell based therapies in regenerative medicine are on the rise but more thorough understanding of stem cell control is necessary for safety reasons.  In the absence of PCL2, stem cells can no longer differentiate into specialized cells regardless of adding stimulating factors to try to push it to differentiate.  Once they re-introduced PCL2 into the stem cells, they were able to drive differentiation again.  By mapping the network of genes that PCL2 regulates, they can trace the steps in the path of a stem cell in becoming one of the many cell types in our body.  University of Toronto scientist, Dr. William Stanford and his team describe their research in the journal Cell Stem Cell.

Stem Cell Prediction: This is a neat study.  Researchers generated an algorithm to predict the future of a stem cell – whether it divides and self-renew as stem cells or produce alternate cell types.  They recorded video of retinal progenitor cells under the microscope to ‘observe’ the cell’s characteristic dynamic behaviour and movements just prior to dividing.  This information was computed to generate a predictive algorithm that was tested to be (amazingly!) 99% accurate in identifying cells that will self-renew as stem cells and 87% correct in predicting a differentiation cell fate.  This may lead to new tools to help scientists isolate pure populations of stem cells for their future studies.  Dr. Michel Cayouette’s group at the Institut de Recherches Cliniques de Montréal presents their work in this week’s edition of Nature Methods.

Genomics of Flesh-eating Disease: The genomic sequences of Streptococcus bacterial strains from past epidemics in Ontario were determined in a study involving Canadian and US researchers.  They identified and compared single nucleotide polymorphisms (SNPs) between the strains and found that they were different by an average of only 49 SNPs.  Each strain, however, also contained unique sequences that could be used for tracking purposes in future outbreaks.  Some genes were highly variable, which is information that they can use to try to understand the bacterial virulence factors at play in gaining an advantage over the infected person.  These comparative pathogenomic studies are invaluable for microbial epidemiology research and for shedding light on new potential targets for antibiotic drugs.  Drs. Donald Low and Allison McGeer at Mount Sinai Hospital participated in the research that is reported in this week’s edition of the Proceedings of The National Academy of Sciences.

Friday Science Review: December 18, 2009

Advancing Cell Research with Proteomic Tools: Advances in technology – particularly in proteomics – are allowing scientists to perform research in more complex systems, a complexity that more closely reflects the situation inside the body.  In the latest trend, researchers can label two different populations of cells with different modified amino acids and use mass spectrometry to distinguish proteins derived from one population versus the other.  This strategy was recently applied to study the EphB2 receptor protein, which plays an important role in a cell’s communication with an adjacent cell expressing ephrin-B1 protein.  Differential labeling allowed the researchers to determine the unique (and similar) molecular signaling network in each cell population as they coordinate their self-organizational activity.  It’s a powerful tool that can be adapted to investigate various systems that cannot be studied in isolation.  The research was performed in Dr. Anthony Pawson’s group at the Samuel Lunenfeld Research Institute and is published in the journal Science.

New Member in the Protein Synthesis Club: After decades of studying and trying to fully understand the mRNA translational machinery for protein synthesis, new components in this complex process continue to be discovered.  The latest is a protein called DHX29, a helicase enzyme that helps to untangle the nucleic acid during the initiation phase of translation.  Down-regulating the enzyme holds up protein synthesis and presents a possible target point to block cancer cells from growing.  Indeed, when the researchers blocked DHX29 in cancer cells, tumour growth was significantly reduced.  Dr. Nahum Sonenberg was the lead author of the study reported in the early online edition of the Proceedings of the National Academy of Sciences.

PS.  Congratulations to Dr. Sonenberg in becoming the 2009 Researcher of the Year for Biomedical and Clinical Research presented by CIHR.

Low Oxygen Response in Cancer Cells:  Within a large tumour, there may be areas of hypoxic microenvironments – regions that are under low oxygen conditions.  Cells in this environment undergo a stress response to try to adapt by carrying out a process called autophagy.  The consequence of this is that the cancer cells ‘get tough’ and subsequently become resistant to radiation therapy.  This recent study investigated one of the possible cell adaptation methods through activation of the unfolded protein response (UPR) pathway.  Induction of two key proteins, MAP1LC3B and PERK, were required for autophagy.  They also demonstrated that inhibition of autophagy resulted in the cells becoming sensitive to hypoxia and irradiation.  Thus, the molecular players involved in autophagy may be good therapeutic targets.  Dr. Bradly Wouters at the Ontario Cancer Institute led the research and reports the findings in the Journal of Clinical Investigation.

Teasing out the Role of E2f Transcription Factors: Members of the E2f family of transcription factors are key regulators that commit cells through the cell division process.  Information in the literature is somewhat perplexing regarding whether they are essential for this process and different studies will support one argument or the other.  New research settles this debate – at least for the E2f1-3 isoform.  Through a series of expression and deletion studies and looking at the different molecular players involved, it was concluded that E2fs are not absolutely required for normal cell division.  The surprise finding is that E2f1-3 is necessary for cell survival in development and its function switches from ‘activator’ in progenitor cells to ‘repressor’ mode in differentiating cells.  The research was conducted at Toronto Western Research Institute by Dr. Rod Bremner’s team and appears in this week’s Nature journal.  The story is corroborated in another similar study in the same issue.

Possible Risk for Diabetes or Heart Disease: A large genome-wide study revealed an association between a polymorphism in the ARL15 gene (ADP-ribosylation factor-like 15) with lower levels adiponectin.  Adiponectin is a fat cell protein and its circulating level is inversely associated with type 2 diabetes and coronary heart disease.  Accordingly, the polymorphism is also associated to some degree with higher risk of heart disease, diabetes and other metabolic related traits.  Surely this requires a more in depth molecular study but this is a good example of how you can sift through large amounts of data from various genome-wide studies and fish out an important finding.  Dr. Brent Richards, now at McGill University, is the corresponding author of the study published in PLoS Genetics.

Genetic Mutation in Intellectual Disability: Approximately 50% of intellectual disability cases are not related to other syndromes.  In these cases, an explanation for the intellectual disability may lie in the gene called TRAPPC9, where a mutation in the gene causes a truncated form of the protein and renders it inactive.  The research team led by Dr. John Vincent at the Centre for Addiction and Mental Health used microarrays to screen a family that had seven members with non-syndromic intellectual disability to map the TRAPPC9 gene.  Additional families with mutations affecting the same gene validated the importance of TRAPPC9, which encodes proteins involved in the NF-κB signaling pathway.  With this new knowledge, researchers can screen patients or family members to track the mutation and also dig deeper into the mechanisms in the brain that affects cognitive development.  The study appears in the American Journal of Human Genetics.

Friday Science Review: October 16, 2009

A mixed bag of research reports but nonetheless important and significant…

How MS Drug Works: Glatiramir Acetate (COPAXONE®, Teva Pharmaceuticals) is used for the treatment of patients with Multiple Sclerosis, however, it is not clear how this drug works.  In this new study, researchers demonstrate that glatiramir acetate can regulate the formation of myelin, the protective sheath around nerve fibers that is compromised in MS patients.  Glatiramir acetate induces the formation of helper immune cells that produce nerve promoting molecules, which in turn stimulate the myelin repair process. The study was led by Dr. V. Wee Yong at the University of Calgary and appears in this week’s issue of The Proceedings of the National Academy of Sciences.

New Target to Fight Diabetes: In genetic knockouts of the Lkb1 gene specifically in beta cells, the insulin producing units in the pancreas, the knockout mice exhibited an increased number of beta cells that were also larger than normal with greater amounts of insulin.  When they challenged the knockout mice with a high-fat diet to try to induce diabetes, the mice responded and kept blood glucose levels down.  Lkb1 is a tumor suppressor gene that was also known to be involved in energy metabolism but it was unclear whether the Lkb1 protein was associated with diabetes.  Dr. Robert Screaton’s group at the Children’s Hospital of Eastern Ontario Research Institute answered this question in a report appearing in this week’s Cell Metabolism.  Also noteworthy is that a research team from Israel published a similar study leading to the same conclusions.  With these surprising and dramatic results, Lkb1 may represent another therapeutic avenue to treat or prevent diabetes.

Sialyltransferase Crystal Structure Solved: Many important proteins, lipids or sugars are modified by the addition of sialic acid and these steps are essential for a number of processes including cell recognition, cell adhesion and immunogenicity.  The key enzyme responsible for catalyzing this reaction is a set of related sialyltransferases (ST).  In a Nature Structural and Molecular Biology report published this week, Dr. Natalie Strynadka (University of British Columbia) describes solving the crystal structure of ST and provides the first detailed understanding of the enzyme.  Without getting into any molecular jargon, suffice it to say that the structural data brings insight into how the enzyme works and how it achieves specificity, which is useful knowledge for developing prospective inhibitors.

Power of Pheromones: Researchers removed the pheromone-producing cells in fruit flies (male or female) and found that these flies were extremely attractive to normal male fruit flies and also flies of other related species.  This contradicts the notion that these chemical signals simply attract one individual to another.  Instead, they are part of a complex signaling system used by the flies to recognize and distinguish sexes and species.  Other unusual behaviour by male fruit flies without pheromones included trying to copulate with each other’s heads.  Dr. Joel Levine and his team at the University of Toronto (Mississauga) describe their research in detail in this week’s edition of Nature.

Beta-globin Switch: A proteomics screen was used to identify the enzyme G9a as the interacting partner of NF-E2, which act together to control expression of the beta-globin genes in red blood cell development.  This study provides a clearer understanding of the molecular determinants controlling embryonic expression of beta-globin where G9a acts as a repressor and its transition to adult beta-globin expression where G9a promotes expression.  The research team at the Ottawa Hospital Research Institute was lead by Dr. Marjorie Brand and the study appears in the early online edition of the Proceedings of the National Academy of Sciences.

Friday Science Review: September 11, 2009

Two great medical discoveries…

Stayin’ Alive:  During a stroke, for example, neurons deprived of oxygen undergo cell death.  In a recent discovery lead by Dr. Michael Tymianski’s team at the Krembil Neuroscience Centre at Toronto Western Hospital, the protein TRPM7 was found to play a critical role in mediating this detrimental effect.   After suppressing TRPM7 expression in a localized region of a rat’s brain, they simulated a stroke by cutting off blood flow to the brain for 15 minutes.  The subsequent analysis revealed a complete lack of tissue damage compared to rat brains expressing TRPM7.  The resistance to death by cells lacking TRPM7 even preserved the brain’s cognitive function and memory performance following the ‘stroke’.  This may have tremendous implications for preventing further cell damage following ischemia in any tissue and is not necessarily limited to the brain, although it is yet to be tested elsewhere in the body

Details of the discovery are reported in the latest edition of Nature Neuroscience.

Insulin Resistance Gene Discovery: An international effort led by Dr. Robert Sladek and Dr. Constantin Polychronakos at McGill University performed a genome-wide comparison and identified a single nucleotide variation in the genetic region near the IRS1 gene that is associated with insulin resistance and hyperinsulinemia.

Dr. Sladek explains it best:

“It’s a single-nucleotide polymorphism (SNP, pronounced ‘snip’), a single letter change in your DNA,” said Sladek. “What’s interesting about this particular SNP is that it’s not linked genetically to the IRS1 gene in any way; it’s about half-a-million base-pairs away, in the middle of a genetic desert with no known genes nearby. In genetic terms, it’s halfway from Montreal to Halifax. And yet we can see that it causes a 40-per-cent reduction in the IRS1 gene, and even more important, a 40-per-cent reduction in its activity. Which means that even if insulin is present, it won’t work.”

IRS1 is known to be the key signalling protein involved in the cell’s initial response to insulin.  This recently discovered variant allele affects the level of IRS1 protein expressed and reduces the capacity of the cells to respond to insulin. Unlike other diabetes risk genes that affect insulin production in the body, this is the first that is known to suppress insulin stimulation in the cells.

The research article appears in the early online edition of Nature Genetics.

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